A broad range of natural and synthetic polymers with widely varying chemical and physical properties are known. For some applications, a combination of physical and/or chemical properties exhibited by different types of polymers may be desirable. Such combinations may provide such properties as suitable flexibility, elasticity, strength, impact resistance, toughness, thermal stability, degradability/bioabsorbability, or a combination of two or more of the foregoing. To achieve such combinations of properties, there are a number of approaches including, but not limited to, forming copolymers (e.g., by combining multiple monomer types or by grafting one type of polymer to another), and combining two or more types of polymers to create a blend. In some applications, both strategies are employed (e.g., a copolymer is prepared and blended with another polymer).
Blending (or compounding) is a relatively common approach for commercial production of various types of polymer-containing products, including, e.g., medical/surgical devices such as stents, screws, pins, staples, and the like. Blends are prepared by providing the two or more polymers independently and mixing the two or more polymers. See White and Bumm, Polymer Blend Compounding and Processing, in Encyclopedia of Polymer Blends: Vol. 2: Processing, 1st Ed. (2011). Blending can be done in solution (by combining the two or more polymers in a solvent and then removing the solvent) or, more commonly, in the absence of solvent (by combining the polymers at elevated temperature, e.g., above the glass transition temperature of the polymers so that they are soft and can be mixed, and then cooling the resulting mixture).
However, such blending techniques require further processing of prepared polymers, which increases production costs and adds extra levels of complexity, including the risk of excessive polymer degradation. With specific regard to blending in solvents, solvent and non-solvent affinities between species can, in some cases, result in undesirable, thermodynamically driven separation of the polymer species upon solvent removal. Furthermore, with blending in solvents, the solvent must be removed to provide the solid polymer blend, which can, in some cases result in degradation of the polymer due to the application of heat. With specific regard to blending in melts, it may be difficult in some applications to obtain substantially homogenous mixing of the two or more polymers, even when polymers are largely miscible with each other. Accordingly, it would be beneficial to provide additional processes for providing polymer blends.